In the prior art, there are three traditional structures for a LIN transmitter: closed-loop-controlled transmitter; open-loop-controlled transmitter; and DAC (Digital-to-Analog Converter)-controlled transmitter.
Generally speaking, the prior art closed-loop-controlled transmitter shows good EMI (ElectroMagnetic Interference) characteristics but poor immunity to RF (Radio Frequencies). The closed-loop-controlled transmitter uses feedback in its design. As a rule, however, the use of feedback has become forbidden in later designs of LIN transmitters, because the use of feedback may cause unexpected operation.
The open-loop-controlled transmitter has better immunity to RF than the close-loop-controlled transmitter, but worse EMI characteristics.
DAC-controlled transmitters are a variation of an open-loop transmitter. The DAC-controlled structure can theoretically be made acceptable for both RF and EMI performance. However, in practice, circuit complexity becomes an issue and a practical realization of the DAC-controlled transmitter fails to measurably improve performance.
What is desired, therefore, is a relatively simple LIN transmitter design that shows real improvement in RF and EMI performance, as well as good immunity to ISO2 and ISO3a pulses (See the ISO 7637 standard for the definition of these pulses). This immunity is not present in the prior art.